The goal of this project is to identify the products of genes involved in mitosis. We have chosen to work with a single eukaryotic organism Aspergillus nidulans, primarily because it has a well-known and powerful genetic system. A large number of mitotic mutants have been identified in Aspergillus by our laboratory (Morris (1976) Genet. Res. Cambr. 26, 237) we will as mutations in the genes for A- and B-subunits of tubulin (Sheir-Neiss, Lai & Morris (1978) Cell 15, 639; Morris, Lai and Oakley (1979) Cell 16, 437). We intend to continue to examine the interrelations between these genes genetically and to develop new methods for identifying gene products other than tubulin that are involved in mitosis.